Various organopolysiloxane compositions have been used for imparting non-stickiness to the surface of a substrate. Conventional organopolysiloxane compositions for this use are roughly divided into (1) a solution comprising a hydroxyl-terminated diorganopolysiloxane, an organopolysiloxane having an Si--H bond and/or an organoalkoxysilane, an organotin compound, and an organic solvent, (2) an aqueous emulsion comprising a hydroxyl-terminated diorganopolysiloxane, an organopolysiloxane having an Si--H bond and/or an organoalkoxysilane, polyvinyl alcohol, etc., emulsified in water, (3) a composition comprising an organopolysiloxane having at least two vinyl groups per molecule, an organopolysiloxane having an Si--H bond, platinum or a platinum compound, and an organic solvent and/or a curing inhibitor.
Although these organopolysiloxane compositions are excellent in providing a non-sticking film on a substrate, the cured silicone layer formed on a rubber or plastic substrate comes off the substrate easily. Further, the composition (3), when applied to a substrate made of natural rubber, general synthetic rubber or soft polyvinyl chloride, is often hindered from curing because a vulcanizer, a vulcanization accelerator or a plasticizer contained in the substrate ruins the activity of the platinum component.
In order to overcome these problems, and particularly to make a rubber or plastic surface non-sticky, water repellent and abrasion resistant, JP-A-54-43891 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") teaches a composition comprising (i) an organopolysiloxane having at least two monovalent hydrocarbon groups substituted with an epoxy-containing group, such as a glycidoxy group and/or an epoxycyclohexyl group, bonded to the silicon atom in the molecule and (ii) an alkoxysilane and/or an alkoxysiloxane each having an alkoxy group bonded to the silicon atom and a substituted or unsubstituted amino group bonded to the silicon atom via at least one carbon atom. According to the disclosure, the composition cures into a slippery film, and addition to the composition of (iii) a diorganopolysiloxane blocked with a hydroxyl group at both terminals thereof, (iv) an organohydrogen polysiloxane and (v) a fatty acid metal salt brings about improved surface slip characteristics, adds flexibility to the cured film, and increases the rate of heat curing.
JP-A-56-78960 proposes a composition comprising (i) a mixture and/or a partial reaction product of an amino-containing silane and/or siloxane and an epoxy-containing silane and/or siloxane and (ii) a diorganopolysiloxane with its both terminals blocked with a hydroxyl group, to which are added (iii) an organohydrogen polysiloxane and (iv) a fatty acid metal salt to improve the rate of curing in room temperature curing and to inhibit whitening of the cured film with time.
When applied to a rubber substrate, these compositions provide a coating film excellent in non-stickiness, water repellency and abrasion resistance but do not always exhibit satisfactory adhesion to natural or organic rubber substrates. In particular, it has been demanded to improve the adhesion to EPDM articles such as a sheet and molded sponge.